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MA 12 P. 



CHAP, or fruit, which in many kinds of plants encloses more than 

 one seed, but in grasses and some other plants only one. We 

 may therefore define the seed as a miniature living plant and 

 its food-supply, wrapped in a protective envelope. The pro- 

 duction of seed is a provision of nature to enable a living 

 plant to remain dormant during a period when climatic con- 

 ditions, as, for example, an intensely cold winter or a long, 

 dry summer, are unfavourable to its existence as an active 

 organism. 



63. The Embryo and Endosperm. — The embryo (Fig. 15B) 

 is the vital part of a seed ; it is a living, though dormant, 

 plant-in-embryo. The embryo comprises all the essential 



Fig. 15. — Embryo and endosperm of maize. A, Section through maize grain 

 showing relative position of embryo and endosperm, a, hull; b, aleurone 

 layer ; c, horny endosperm ; J, white starchy endosperm ; e, plumule ; f, radicle ; 

 g, scutellum. B, Embryo removed. C, Germinating embryo. 



organs of growth, i.e. the radicle which develops into the root 

 of the plant ; the cotyledon or seed-leaf ; and the plumule or 

 young shoot, which develops into stem and leaves. In maize 

 and other grasses the growing embryo absorbs the endosperm 

 through a special organ, the scutellum (so named from its 

 shield-like shape), which in maize can readily be seen with a 

 low-power microscope. The embryo of the maize-grain lies 

 to one side of the endosperm (Fig. 15A) ; as the grain stands 

 on the ear, the embryo is on the upper side of the grain, i.e. 

 facing toward the tip of the ear, its position being indicated 

 by an oval depression in the grain. 



